The specific aims are: Observational study: Quantitate the bone loss in premenopausal women undergoing adjuvant chemotherapy for breast cancer. This will be achieved by measuring bone density at spine, hip and total body before and at regular intervals following chemotherapy for breast cancer in 200 pre- menopausal women. 2) Intervention study: Conduct a two year double blind placebo controlled trial of the effect of a bisphosphonate on bone density in 100 premenopausal women rendered menopausal by treatment with adjuvant chemotherapy for breast cancer.